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On spare parts demand and the installed base concept: A theoretical approach
No full textFrenk, J.B.G./0000-0002-2161-8681Original Equipment Manufacturers (OEMs) aim to design their service supply chain before the introduction of their products to maximize their aftersales business revenues, reduce waste and achieve sustainability. In this study, we develop a stochastic model that unifies the installed base, i.e., the number of products in use, spare parts demand, and the number of discarded products within a single modeling framework based on three product characteristics: sales rate, usage time, and failure rate. Our model describes the installed base and spare part demand evolution over the entire life cycle of a parent product using stochastic point processes. At the same time we propose under very general assumptions on the cdf of the usage time and the mean arrival functions of the sales and failure processes an easy bisection procedure to compute the time at which the expected installed base and rate of the expected demand for spare parts is maximal. Our numerical experiments show that the volume of aftersales services increases in the expected usage time if the products face an increasing failure rate. The same experiments also reveal a 20 percent shift of the time at which the expected installed base is maximal in case the expected usage time is increased threefold. At the same time, we observe a boosting effect of the intensity of the sales process on this point in time
Index Composition Changes Around the World: a Comprehensive Literature Review
No full textThis paper aims to provide a comprehensive literature review on composition changes for benchmark indexes not only for popular indexes such as the S&P 500 but for also global counterparts both in the developed world and the emerging market realm. By shedding light on the phenomena at play for index changes we seek to provide an overview starting from the roots of the literature to modern day works that reflect the current state of the topic and also where it is going. The theme of our study is orientated around the discussion range between information effects associated with index inclusions and exclusions, implications for liquidity, price pressure and demand shocks resulting with demand curve shifts and slopes for the demand curves of stocks and other subtopics such as thematic index composition changes. We dive into whether index composition changes en masse are rooted in information and/or demand driven explanations around the world
Yerel Yönetimlerin Mekansal Müdahalelerle Kamusal Alana Etkisi: Beyazıt Meydanı Örneği
No full textBu çalışmada, yerel yönetimlerin mekansal müdahalelerinin bir kamusal alan olan Beyazit Meydanı'nın dönüşümüne olan etkileri incelenmiştir. Meydanlar, ortak yaşama pratiklerinin en iyi gözlenebildiği alanlar olarak bulundukları toplumun kamusal yaşam biçimini yansıtırlar. Beyazıt Meydanı tarihsel süreçte hem bir kamusal alan olarak ortaya çıkmasıyla hem de dönemin ve toplumun koşullarından etkilenerek biçimlenmesiyle inceleme sahası olarak belirlenmiştir. Yerel yönetimlerin kent politikası, dönemin siyasi, ekonomik ve toplumsal koşulları tarafından şekillendirilir. Bu açıdan hem Türkiye'de hem dünyada 1980'lerle başlayan değişim dönemi, Türkiye'de 1984 yerel seçimleri baz alınarak başlangıç yılı olarak seçilmiş ve 2019 yılındaki yerel seçimler dışarıda bırakılarak bu döneme kadar değerlendirilmiştir. Yerel yönetimlerin İstanbul özelinde beş yıllık idari süreçleri, bağlı bulundukları siyasi partiler, dönemin koşulları ve kente yaklaşımları ele alınarak değerlendirilmiştir. Beyazıt Meydanı'nın yerel yönetimlerin müdahaleleriyle yaşadığı değişim, gazete haberlerine yansıyan bilgilerden, büyükşehir ve ilçe belediyesinin yıllık faaliyet raporlarından, kentsel tasarım yarışmalarının projelerinden, ilgili dönemde hazırlanmış üst ölçek planlardan yola çıkarak incelenmiştir. Beyazıt Meydanı, yerel iktidarlar olan belediyelerin her dönem ilgilendikleri bir kamusal alan olmuştur. Dönemin gazete haberlerine yansıyan başlıklarında ve meydanla ilgili tarihi boyunca yapılan düzenlemelerde bu görülmektedir.In this study, the effects of the spatial interventions of local governments on the transformation of Beyazit Square, a public space, were examined. Squares reflect the public lifestyle of their society as the areas where common living practices can be best observed. Therefore, Beyazit Square has been determined as a field of study both by its emergence as a public space in the historical process and by being shaped by the conditions of the period and society. The city policy of local governments is shaped by the period's political, economic, and social conditions. In this respect, the period of change that started in the 1980s, both in Turkey and in the world, was chosen as the starting year based on the 1984 local elections in Turkey, and the 2019 local elections were excluded and evaluated until this period. The five-year administrative processes of local governments in Istanbul, the political parties they are affiliated with, the conditions of the period, and their approach to the city were evaluated. The change that Beyazit Square has experienced with the interventions of the local governments has been examined based on the information reflected in the newspaper news, the annual activity reports of the metropolitan and district municipalities, the projects of the urban design competitions, and the upper scale plans prepared in the relevant period. Beyazit Square has always been a public space that municipalities, which are local governments, have been interested in. This is seen in the headlines reflected in the newspaper news of the period and the arrangements made throughout the history of the square
For Centenary of the Lausanne Treaty: Re-Interpretation and Re-Implementation of Linguistic Minority Rights of Lausanne
No full textThe Treaty of Lausanne was signed on 24th July 1923 as a peace treaty that ended the first world war for Turkey and the allied powers. In a section entitled "protection of minorities", it provides rights for minorities. However, the beneficiaries of minority rights in Lausanne are more narrow than those provided in other treaties and declarations of the time. With a legal basis in domestic law, Turkey traditionally applied the rights provided in the Lausanne Treaty only for three so-called non-Muslim groups, i.e. Greeks, Armenians and Jews. Neither the Turkish delegation nor the members of the allied forces' delegations could foresee that some members of the Muslim groups of 1923 might quit Islam in the future and recourse to Lausanne rights as new beneficiaries. This article, by referring to preparatory works of the Treaty, examining its legal validity internationally and nationally, and applying interpretative principles of international treaties, argues for the extension of Lausanne rights to other groups via re-interpretation and re-implementation. © 2023 Olgun Akbulut
Joint Visible Light Communications and Positioning with Dimming
No full text31st IEEE Conference on Signal Processing and Communications Applications (SIU) -- JUL 05-08, 2023 -- Istanbul Tech Univ, Ayazaga Campus, Istanbul, TURKEYIn this paper, a novel visible light communication (VLC) and three-dimensional (3D) positioning (VLP) algorithm based on spatial modulation (SM) with dimming capability is proposed. With the help of the signal and pilot symbols observed by a user with two photodetectors (PD) on the receiver, the detection of the transmitted data with the estimated channel and dimming coefficients is performed, and at the same time, the position of the user represented in 3D is determined. The computer simulations conclude that the root mean square (RMS) values of the proposed algorithm in 3D position determination are very low, and the bit error rate (BER) performance is very high.IEEE,TUBITAK BILGEM,Turkcel
Factors Affecting the Purchase Intention of Over the Counter Products in the Self Care Actions of Consumers
No full textPurpose - Within the framework of the theory of planned behavior (TPB), this study aims to investigate which factors affect consumers' purchase intention with regard to over-the-counters (OTCs), focusing on personal factors, including health consciousness and risk aversion, as well as rational factors, consisting of the level of knowledge, price consciousness and involvement in the purchase intentions. Design/methodology/approach - Due to the necessity of finding the most crucial industry-specific indicators, it was decided to carry out two-stage research based on qualitative preliminary research and the main study. The findings obtained from the qualitative studies were integrated with insights gleaned from the literature to finalize the study's conceptualmodel. Themain study was based on a descriptive research design, and data were collected through an online survey. Structural equationmodelingwas themain technique used to test themodel. Findings - Health consciousness, level of knowledge and involvement in consumer purchase intentions affect either attitude or perceived behavioral control. Moreover, attitudes toward OTCs and perceived behavioral control were significant predictors of purchase intentions for OTC drugs. At the same time, subjective norms did not have a significant effect. Practical implications - Knowing what influences consumer purchase intentions contributes to developing more effective marketing strategies and actions. Originality/value - This study took an integrative approach to understanding the effect of personal and rational factorswithin the TPB framework for a changing tendency in consumer behavior of specific product categories.Emerging Sources Citation Inde
Turkish Remakes of Korean Tv Dramas
No full textIn the complex sphere of global television dramas, South Korea has emerged as a regional force in the last few decades, followed by Turkey in the 2000s. Turkish TV dramas are sold to over 140 countries throughout the world, demanding a constant supply of new content, met in part by remakes. While Korean productions receive limited distribution in Turkey, a significant number of these have been remade by Turkish companies. Since 2013, Korean dramas have replaced Hollywood series as the primary source of adaptations for Turkish dramas. There appear to be shared sensibilities that make the Korean stories palatable to Turkish audiences, but more significantly, certain production practices make Korean sources a more viable choice than Hollywood series for Turkish producers. This article explores these sensibilities from an industrial point of view, employing testimonies from leading industry informants who have been instrumental in introducing Korean source material to Turkish television
A Two-Phase Pattern Generation and Production Planning Procedure for the Stochastic Skiving Process
No full textAltay, Ayca/0000-0001-6066-5336; Samanlioglu, Funda/0000-0003-3838-8824The stochastic skiving stock problem (SSP), a relatively new combinatorial optimization problem, is considered in this paper. The conventional SSP seeks to determine the optimum structure that skives small pieces of different sizes side by side to form as many large items (products) as possible that meet a desired width. This study studies a multiproduct case for the SSP under uncertain demand and waste rate, including products of different widths. This stochastic version of the SSP considers a random demand for each product and a random waste rate during production. A two-stage stochastic programming approach with a recourse action is implemented to study this stochastic NP-hard problem on a large scale. Furthermore, the problem is solved in two phases. In the first phase, the dragonfly algorithm constructs minimal patterns that serve as an input for the next phase. The second phase performs sample-average approximation, solving the stochastic production problem. Results indicate that the two-phase heuristic approach is highly efficient regarding computational run time and provides robust solutions with an optimality gap of 0.3% for the worst-case scenario. In addition, we also compare the performance of the dragonfly algorithm (DA) to the particle swarm optimization (PSO) for pattern generation. Benchmarks indicate that the DA produces more robust minimal pattern sets as the tightness of the problem increases
Evaluation of Public Transportation Systems for Sustainable Cities Using an Integrated Fuzzy Multi-Criteria Group Decision-Making Model
No full textIn this era of increasing demand for mobility and rapid urban growth, there is a pressing need for a public transit system that is safe, fast, reliable, well-connected, and sustainable. Furthermore, it is essential to reduce the external costs associated with urban transportation, including environmental pollution, noise, congestion, and accidents, to foster sustainable cities. Choosing the right urban transportation system can meet this goal, but it is not an accessible business for decision-makers in the face of several conflicting criteria and ambiguities in the evaluation process. To cope with this, the current paper suggests a multi-criteria group decision-making (MCGDM) framework consisting of fuzzy BWM (Best-Worst method) and fuzzy MAIRCIA (Multi-Attribute Ideal-Real Comparative Analysis) techniques. This extended MCGDM approach has been applied to evaluate six urban transport systems, namely, Trams, Light Rail Trams, Metro (Subway), Bus Rapid Transport, Commuter Trains, and Public Buses based on 11 selection criteria which we have determined after consultation with highly experienced professionals. The fuzzy BWM technique is employed to identify the weights of the criteria. The fuzzy MAIRCA technique is utilized for ranking the alternatives using the calculated weights of the criteria. The proposed approach's validation has been examined with an extensive robustness check. The study is conducted from a general perspective, i.e., not restricted to a particular city. However, with the identified selection criteria, the proposed decision-making procedure can be repeated for a specific city considering any specific requirements, constraints, or limitations of that city
Evaluation of the Special Warehouse Handling Equipment (turret Trucks) Using Integrated Fucom and Waspas Techniques Based on Intuitionistic Fuzzy Dombi Aggregation Operators
No full textTurret trucks used for special warehousing operations have exceptional abilities, qualifications, and working principles than other warehousing handling equipment. Also, at the same time, if decision-makers cannot select as proper to needs, the cost of being idle of these kinds of machines is very high. According to the comprehensive literature review and the paper's findings, evaluating turret trucks is complex, complicated, and time-consuming for decision-makers, as many conflicting criteria and uncertainties affect the evaluation processes. Hence, it is required to employ a practical, powerful, and practical multi-criteria decision-making (MCDM) approach that can handle ambiguities to solve these kinds of problems. For this purpose, the current paper proposes an extended version of a hybrid decision-making tool consisting of FUCOM (Full Consistency Method) and the WASPAS (Weighted Aggregated Sum Product Assessment) technique with the help of the intuitionistic fuzzy Dombi aggregation operators. It can help to select the appropriate turret trucks that can help reduce the costs of remaining idle and provide economic effectivity of logistics and warehousing operations. According to the outcomes of the suggested model, the width, lift motor power and lift height of the turret trucks are the most critical and influential criteria, as they determine the corridor width, accordingly space utilization, warehousing capacity, and unit warehousing costs. Finally, the intuitionistic fuzzy model is applied to solve the turret truck selection problems. A comprehensive sensitivity analysis consisting of three phases was performed to test the validation of the proposed model and its obtained results. The sensitivity analysis results approve the proposed model's applicability and validity. Thus, the analysis results validated that the proposed approach is a robust and practical MCDM framework, and its results are accurate and reasonable